Polyphosphate-accumulating Bacteria Research Articles

Primary settling changes the microbial community of influent wastewater to wastewater treatment plants

The continuous immigration of bacteria in influent wastewater strongly impacts the microbial community of activated sludge (AS) in wastewater treatment plants (WWTP), both in terms of species composition and their abundance. Therefore, it is of interest to elucidate the route of immigrating bacteria into the biological tanks, including the effect of primary settlers. These are commonly used pretreatment units that can possibly selectively increase or reduce the relative abundance of certain bacteria. Species-level identification of the microbial composition of influent wastewater before and after primary settling was carried out in four full-scale municipal WWTPs biweekly over one year by 16S rRNA gene amplicon sequencing. Overall, 37–49% of incoming COD was removed in the primary settlers. Most genera and species were present in the wastewater to all four plants and the trend of these were investigated across the primary settlers. Approximately 50% of the genera had the same trend across at least three WWTPs. Few genera significantly increased in relative read abundance (3.7%) after settling, while 22.3% showed a significant reduction in relative abundance. We investigated process-critical species in AS, such as known nitrifiers, polyphosphate-accumulating organisms, and filamentous bacteria. Most taxa were affected similarly in all WWTPs including multiple genera involved in bulking in AS. However, some genera, e.g., important polyphosphate-accumulating bacteria, had inconsistent trends across WWTPs, suggesting that the characteristics of the wastewater are important for the trend of some bacteria through primary settling. In all cases, primary settling changed the microbial community of the influent wastewater, posing an obvious candidate for upstream control to optimize the assembly of the microbial communities in activated sludge.

Microbial communities associated with phosphogenic sediments and phosphoclast‐associated DNA of the Benguela upwelling system

The processes that lead to the precipitation of authigenic calcium phosphate minerals in certain marine pore waters remain poorly understood. Phosphogenesis occurs in sediments beneath some oceanic upwelling zones that harbor polyphosphate-accumulating bacteria. These bacteria are believed to concentrate phosphate in sediment pore waters, creating supersaturated conditions with respect to apatite precursors. However, the relationship between microbes and phosphorite formation is not fully resolved. To further study this association, we examined microbial community data generated from two sources: sediment cores recovered from the shelf of the Benguela upwelling region where phosphorites are currently forming, and DNA preserved within phosphoclasts recovered from a phosphorite deposit along the Benguela shelf. iTag and clone library sequencing of the 16S rRNA gene showed that many of our sediment-hosted communities shared large numbers of phylotypes with one another, and that the same metabolic guilds were represented at localities across the shelf. Sulfate-reducing bacteria and sulfur-oxidizing bacteria were particularly abundant in our datasets, as were phylotypes that are known to carry out nitrification and the anaerobic oxidation of ammonium. The DNA extracted from phosphoclasts contained the signature of a distinct microbial community from those observed in the modern sediments. While some aspects of the modern and phosphoclast communities were similar, we observed both an enrichment of certain common microbial classes found in the modern phosphogenic sediments and a relative depletion of others. The phosphoclast-associated DNA could represent a relict signature of one or more microbial assemblages that were present when the apatite or its precursors precipitated. While these taxa may or may not have contributed to the precipitation of the apatite that now hosts their genetic remains, several groups represented in the phosphoclast extract dataset have the genetic potential to metabolize polyphosphate, and perhaps modulate phosphate concentrations in pore waters where carbonate fluorapatite (or its precursors) are known to be precipitating.

Polyphosphate-Accumulating Bacteria: Potential Contributors to Mineral Dissolution in the Oral Cavity.

ABSTRACTBacteria that accumulate polyphosphates have previously been shown to dynamically influence the solubility of phosphatic minerals in marine settings and wastewater. Here, we show that dental plaque, saliva, and carious lesions all contain abundant polyphosphate-accumulating bacteria. Saturation state modeling results, informed by phosphate uptake experiments using the model organism Lactobacillus rhamnosus, which is known to inhabit advanced carious lesions, suggest that polyphosphate accumulation can lead to undersaturated conditions with respect to hydroxyapatite under some oral cavity conditions. The cell densities of polyphosphate-accumulating bacteria we observed in some regions of oral biofilms are comparable to those that produce undersaturated conditions (i.e., those that thermodynamically favor mineral dissolution) in our phosphate uptake experiments with L. rhamnosus. These results suggest that the localized generation of undersaturated conditions by polyphosphate-accumulating bacteria constitutes a new potential mechanism of tooth dissolution that may augment the effects of metabolic acid production.IMPORTANCE Dental caries is a serious public health issue that can have negative impacts on overall quality of life and oral health. The role of oral bacteria in the dissolution of dental enamel and dentin that can result in carious lesions has long been solely ascribed to metabolic acid production. Here, we show that certain oral bacteria may act as a dynamic shunt for phosphate in dental biofilms via the accumulation of a polymer known as polyphosphate—potentially mediating phosphate-dependent conditions such as caries (dental decay).

Functional evaluation of pollutant transformation in sediment from combined sewer system

In this study, a pilot combined sewer system was constructed to characterize the pollutant transformation in sewer sediment. The results showed that particulate contaminants deposited from sewage could be transformed into dissolved matter by distinct pollutant transformation pathways. Although the oxidation-reduction potential (ORP) was varied from −80 mV to −340 mV in different region of the sediment, the fermentation was the dominant process in all regions of the sediment, which induced hydrolysis and decomposition of particulate contaminants. As a result, the accumulation of dissolved organic matter and the variation of ORP values along the sediment depth led to the depth-dependent reproduction characteristics of methanogens and sulfate-reducing bacteria, which were existed in the middle and deep layer of the sediment respectively. However, the diversity of nitrifying and polyphosphate-accumulating bacteria was low in sewer sediment and those microbial communities showed a non-significant correlation with nitrogen and phosphorus contaminants, which indicated that the enrichment of nitrogen and phosphorus contaminants was mainly caused by physical deposition process. Thus, this study proposed a promising pathway to evaluate pollutant transformation and can help provide theoretical foundation for urban sewer improvement.

Removal of phosphate by Staphylococcus aureus under aerobic and alternating anaerobic–aerobic conditions

ABSTRACTEutrophication of water bodies due to phosphate enrichment is an ecological problem. Phosphate is removed from wastewaters by enhanced biological phosphate removal worldwide by phosphate accumulating organism. In order to understand the process of treatment, the existing microbial community and its metabolism of phosphate removal are studied widely. This study focuses on the isolation of polyphosphate-accumulating bacteria from different environments and studying their phosphate removal capacity with different carbon supplements under varying culture conditions. The total heterotrophic bacterial population from the diverse environments showed the existence of phosphate-accumulating bacteria. Among them, Staphylococcus aureus removed 81% of phosphate in a polyphosphate-accumulating medium with storage of 93 mM polyphosphate internally. Among the different carbon sources provided, glucose induced a net specific growth rate of 0.816/d. S. aureus removed 70% of phosphate with a phosphate uptake rate of 6.29 mg PO4/g cells and a growth yield of 0.2 g cells/g glucose consumed when 1 g/L glucose was provided. Furthermore, when 2 g/L glucose was provided, 78% of phosphate was removed with a phosphate uptake rate of 13.24 mg PO4/g cells and a growth yield of 0.4 g cells/g glucose consumed under aerobic condition. S. aureus showed enhanced phosphate removal under aerobic condition in the presence of glucose.

Performance of an Ultraviolet Mutagenetic Polyphosphate-Accumulating Bacterium PZ2 and Its Application for Wastewater Treatment in a Newly Designed Constructed Wetland.

Total phosphorus (TP) removal performance and application for wastewater treatment of polyphosphate-accumulating bacteria (PAB) in constructed wetlands (CWs) were investigated. In this study, a novel isolated ultraviolet (UV) mutant PZ2 with phosphate-accumulating ability was screened from domestic wastewater and identified as Pseudomonas putida by 16S ribosomal DNA (rDNA) sequencing analysis. The TP removal performance of PZ2 in the synthetic wastewater reached the highest of 93.95% within 45h. Two vertical subsurface flow CWs planted with two aquatic macrophytes Canna indica and Acorus calamus were newly designed. After inoculating PZ2 into two CWs within 45h, the average chemical oxygen demand (COD), TP, and ammonia-nitrogen (NH3-N) removal efficiencies reached 68.50, 60.22, and 66.81%, respectively. Vegetation type and filter size significantly influenced the TP removal capability of PZ2 in CWs. Meanwhile, considerable qualitative differences were found in the pollutant removal efficiencies of PZ2 with and without CWs in synthetic wastewater. These results could also indicate potential applications of the UV mutagenesis in PAB isolation and the newly designed CWs in wastewater treatments.

Intracellular Accumulation of Glycine in Polyphosphate-Accumulating Organisms in Activated Sludge, a Novel Storage Mechanism under Dynamic Anaerobic-Aerobic Conditions.

Dynamic anaerobic-aerobic feast-famine conditions are applied to wastewater treatment plants to select polyphosphate-accumulating organisms to carry out enhanced biological phosphorus removal. Acetate is a well-known substrate to stimulate this process, and here we show that different amino acids also are suitable substrates, with glycine as the most promising. (13)C-labeled glycine and nuclear magnetic resonance (NMR) were applied to investigate uptake and potential storage products when activated sludge was fed with glycine under anaerobic conditions. Glycine was consumed by the biomass, and the majority was stored intracellularly as free glycine and fermentation products. Subsequently, in the aerobic phase without addition of external substrate, the stored glycine was consumed. The uptake of glycine and oxidation of intracellular metabolites took place along with a release and uptake of orthophosphate, respectively. Fluorescence in situ hybridization combined with microautoradiography using (3)H-labeled glycine revealed uncultured actinobacterial Tetrasphaera as a dominant glycine consumer. Experiments with Tetrasphaera elongata as representative of uncultured Tetrasphaera showed that under anaerobic conditions it was able to take up labeled glycine and accumulate this and other labeled metabolites to an intracellular concentration of approximately 4 mM. All components were consumed under subsequent aerobic conditions. Intracellular accumulation of amino acids seems to be a novel storage strategy for polyphosphate-accumulating bacteria under dynamic anaerobic-aerobic feast-famine conditions.

Removal of low concentration of phosphorus from solution by free and immobilized cells of Pseudomonas stutzeri YG-24

Phosphorus (P) in wastewater is a main factor causing eutrophication, and removal of low concentrations of P (≤ 1.0 mg L − 1 ) is an important, but not fully studied topic. The removal of low content of P is rather difficult or expensive. To develop alternative biological methods for the removal of low concentration P, polyphosphate-accumulating bacteria in surface sediment of Taihu Lake in China were isolated and characterized. Among these bacteria, a Pseudomonas stutzeri strain YG-24 was found to be able to remove 97% to 100% of P in a synthetic wastewater with total P less than 1.0 mg L − 1 . After immobilization by polyvinyl alcohol (PVA)-sodium alginate, this strain still showed high percentage of P removal, and maintained high efficiency in five sample loading cycles. In addition, the immobilized cells displayed better pH-resistance than free cells. The removal of P in overlying water sample collected from Taihu Lake was also satisfactory. These results demonstrated the potential of using immobilized cells of YG-24 to remove low concentrations of P in wastewater treatment.

Dynamics of polyphosphate-accumulating bacteria in wastewater treatment plant microbial communities detected via DAPI (4',6'-diamidino-2-phenylindole) and tetracycline labeling.

Wastewater treatment plants with enhanced biological phosphorus removal represent a state-of-the-art technology. Nevertheless, the process of phosphate removal is prone to occasional failure. One reason is the lack of knowledge about the structure and function of the bacterial communities involved. Most of the bacteria are still not cultivable, and their functions during the wastewater treatment process are therefore unknown or subject of speculation. Here, flow cytometry was used to identify bacteria capable of polyphosphate accumulation within highly diverse communities. A novel fluorescent staining technique for the quantitative detection of polyphosphate granules on the cellular level was developed. It uses the bright green fluorescence of the antibiotic tetracycline when it complexes the divalent cations acting as a countercharge in polyphosphate granules. The dynamics of cellular DNA contents and cell sizes as growth indicators were determined in parallel to detect the most active polyphosphate-accumulating individuals/subcommunities and to determine their phylogenetic affiliation upon cell sorting. Phylotypes known as polyphosphate-accumulating organisms, such as a "Candidatus Accumulibacter"-like phylotype, were found, as well as members of the genera Pseudomonas and Tetrasphaera. The new method allows fast and convenient monitoring of the growth and polyphosphate accumulation dynamics of not-yet-cultivated bacteria in wastewater bacterial communities.

Interactions between calcium precipitation and the polyphosphate-accumulating bacteria metabolism

A sequencing batch reactor that is operated for biological phosphorus removal has been operated under different influent calcium concentrations to study the precipitation process and the possible effects of phosphorus precipitation in the biological phosphorus removal process. Four experiments were carried out under different influent calcium concentrations ranging from 10 to 90 g Ca m −3. The experimental results and the equilibrium study, which are based on the saturation index calculation, confirm that the process controlling the calcium behaviour is the calcium phosphate precipitation. This precipitation takes place at two stages: initially, precipitation of the amorphous calcium phosphate, and later crystallization of hydroxyapatite. Also the accumulation of phosphorus precipitated was observed when the influent calcium concentration was increased. In all the experiments, the influent wastewater ratio P/COD was kept constant. It has been observed that, at high calcium concentration, the ratio between phosphate release and acetate uptake ( P rel/Ac uptake) decreases. Changes in the polyphosphate-accumulating organism (PAO) population and in the glycogen-accumulating organism (GAO) population during the experimental period were ruled out by means of fluorescence in situ hybridization. These results could suggest that PAO are able to change their metabolic pathways based on external conditions, such as influent calcium concentration. The accumulation of phosphorus precipitated as calcium phosphate at high influent calcium concentration throughout the experimental period confirmed that phosphate precipitation is a process that can affect the PAO metabolism.

Use of Laser Microdissection for Phylogenetic Characterization of Polyphosphate-Accumulating Bacteria

Our novel approach for taxonomic identification of uncultured bacteria harboring specific physiological features in complex environmental samples combines cell collection by laser microdissection and subsequent DNA analysis. The newly developed approach was successfully tested for collection and phylogenetic characterization of polyphosphate-accumulating bacteria in activated sludge and lake sediment.

Seven novel species of Acinetobacter isolated from activated sludge.

Thirteen isolates of Acinetobacter were obtained from activated sludge plants in Victoria, Australia. Earlier 16S-23S rDNA genomic fingerprinting and partial 16S rDNA sequence data had suggested that these isolates might contain previously undescribed species. This view was confirmed here. A polyphasic taxonomic approach involving phenotypic characterization, near-complete 16S rDNA sequence data and DNA-DNA hybridization analyses support the view that seven novel genomic species can be differentiated in this group of isolates. However, when fluorescence in situ hybridization (FISH) studies were performed with a 16S-rRNA-targeted probe specific for the genus Acinetobacter, used to identify Acinetobacter in activated sludge plants, all these strains responded positively. This suggests that these isolates would not have been missed in earlier FISH studies where their role as polyphosphate-accumulating bacteria has been questioned. This report describes these isolates and proposes that they be named Acinetobacter baylyi (type strain B2T = DSM 14961T = CIP 107474T), Acinetobacter bouvetii (type strain 4B02T = DSM 14964T = CIP 107468T), Acinetobacter grimontii (type strain 17A04T = DSM 14968T = CIP 107470T), Acinetobacter tjernbergiae (type strain 7N16T = DSM 14971T = CIP 107465T), Acinetobacter towneri (type strain AB1110T = DSM 14962T = CIP 107472T), Acinetobacter tandoii (type strain 4N13T = DSM 14670T = CIP 107469T) and Acinetobacter gerneri (type strain 9A01T = DSM 14967T = CIP 107464T).

Gemmatimonas aurantiaca gen. nov., sp. nov., a gram-negative, aerobic, polyphosphate-accumulating micro-organism, the first cultured representative of the new bacterial phylum Gemmatimonadetes phyl. nov.

A phylogenetically novel aerobic bacterium was isolated from an anaerobic-aerobic sequential batch reactor operated under enhanced biological phosphorus removal conditions for wastewater treatment. The isolation strategy used targeted slowly growing polyphosphate-accumulating bacteria by combining low-speed centrifugations and prolonged incubation on a low-nutrient medium. The isolate, designated strain T-27T, was a gram-negative, rod-shaped aerobe. Cells often appeared to divide by budding replication. Strain T-27T grew at 25-35 degrees C with an optimum growth temperature of 30 degrees C, whilst no growth was observed below 20 degrees C or above 37 degrees C within 20 days incubation. The pH range for growth was 6.5-9.5, with an optimum at pH 7.0. Strain T-27T was able to utilize a limited range of substrates, such as yeast extract, polypepton, succinate, acetate, gelatin and benzoate. Neisser staining was positive and 4,6-diamidino-2-phenylindole-stained cells displayed a yellow fluorescence, indicative of polyphosphate inclusions. Menaquinone 9 was the major respiratory quinone. The cellular fatty acids of the strain were mainly composed of iso-C15:0, C16:1 and C14:0. The G + C content of the genomic DNA was 66 mol%. Comparative analyses of 16S rRNA gene sequences indicated that strain T-27T belongs to candidate division BD (also called KS-B), a phylum-level lineage in the bacterial domain, to date comprised exclusively of environmental 16S rDNA clone sequences. Here, a new genus and species are proposed, Gemmatimonas aurantiaca (type strain T-27T=JCM 11422T=DSM 14586T) gen. nov., sp. nov., the first cultivated representative of the Gemmatimonadetes phyl. nov. Environmental sequence data indicate that this phylum is widespread in nature and has a phylogenetic breadth (19% 16S rDNA sequence divergence) that is greater than well-known phyla such as the Actinobacteria (18% divergence).

Microbial Community Structures of Activated Sludges Dominated with Polyphosphate-Accumulating Bacteria and Glycogen-Accumulating Bacteria

The microbial community structures of anaerobic-aerobic activated sludges, which are dominated with polyphosphate-accumulating bacteria (PABs) and glycogen-accumulating bacteria (GABs), were investigated by quinone profile method and dual staining DAPI (4-, 6-diamidino-2-phenylindol dihydrochloride) with fluorescent in situ hybridization (FISH). For both activated sludges, the predominant bacterial groups were the beta subclass of the Proteobacteria that contained mainly Q-8 as analyzed by the quinone profile method and gram-positive bacteria with a high DNA G+C content based on FISH. A 16S rRNA-targeted oligonucleotide probe (MP2) specific for M. phosphovorus, a known polyphosphate-accumulating bacterium, was also applied to PABs and GABs-enriched activated sludge to evaluate their possible role in the enhanced biological phosphorus removal (EBPR) process. Interestingly, the bacteria that hybridized with the probe specific to M. phosphovorus in the sludge dominated with PABs represent about 6.9 % of the total microorganisms. In the sludge dominated with GABs, these bacteria were about 1.9%. These results suggest its possible involvement in the EBPR process.

The effect of media on evaluating the phosphate uptake capacity of activated sludge bacterial isolates

Since the identification of Acinetobacter calcoaceticus as the primary agent responsible for biological phosphorus removal, much research has been conducted to either confirm or refute this claim. The majority of these studies was conducted under defined laboratory conditions using various artificial media; as a result, many conflicting reports exist regarding the role of A. calcoaceticus and other activated sludge isolates in their possible roles as true polyphosphate-accumulating bacteria. This study was therefore conducted to determine the effect of media type on biological phosphate removal when performed in the laboratory under defined conditions. Five isolates were obtained from a full-scale biological nutrient removal activated sludge system and a previously identified A. calcoaceticus isolate was inoculated into three different media types. The inoculated media were subjected to anaerobic and aerobic conditions to stimulate the phosphate removal mechanism. The test micro-organisms released phosphate, under anaerobic conditions, in the three test media. Synthetic wastewater was found to promote the release of higher concentrations of phosphate by the micro-organisms than in the other two media. During the aerobic phase, phosphate uptake was highest in synthetic wastewater and settled sewage. Due to inconsistencies obtained in the readily biodegradable chemical oxygen demand, total chemical oxygen demand and soluble oxygen demand tests, it was concluded that the medium formulation may skew qualitative or quantitative data regarding biological phosphate removal. It can be concluded that the media used for P uptake studies are of importance as it was observed that the organisms' removal/uptake capabilities were enhanced or reduced depending on the media used.

In situ identification of polyphosphate-accumulating bacteria in activated sludge by dual staining with rRNA-targeted oligonucleotide probes and 4′,6-diamidino-2-phenylindol (DAPI) at a polyphosphate-probing concentration

Polyphosphate-accumulating bacteria in activated sludge samples from an anaerobic/aerobic batch-type reactor for enhanced biological phosphate removal (EBPR) were identified by dual staining with ribosomal RNA-targeted oligonucleotide probes and 4′,6-diamidino-2-phenylindol dihydrochloride (DAPI) at a polyphosphate-probing concentration. The staining with the oligonucleotide probes showed that there were four major bacterial groups in the sludge: the beta subclass of Proteobacteria, Gram-positive bacteria with a high G+C content, the alpha subclass of Proteobacteria, and bacteria belonging to the Cytophaga-Flavobacterium cluster of the Cytophaga-Flavobacterium-Bacteroides phylum. By staining with DAPI, many of the Gram-positive bacteria with a high G+C content and the alpha subclass of Proteobacteria fluoresced bright yellow. These bacteria were considered to accumulate a large amount of polyphosphate.

Physiology and Ecology of Polyphosphate-Accumulating Bacteria.

Enhanced biological phosphorus removal in the processes utilizing anaerobic/aerobic conditions is established by the increase of polyphosphate content in the activated sludge and the withdrawal of the sludge. For stable operation to achieve efficient phosphorus removal, better understanding of the microorganisms including polyphosphate-accumulating bacteria in activated sludge of these processes is required. However, physiology and ecology of bacteria which have an important role in these processes are still unclear. In this paper, the characteristics of important bacteria constructing phosphorus removal processes and the progress of microbial population analysis based on 16S rDNA sequences were introduced.

Anoxic biological phosphorus removal in a full-scale UCT process

Enhanced biological phosphorus removal is based on the selective enrichment of bacteria accumulating inorganic polyphosphate, obtained at a cyclic regime of alternating anaerobic and aerobic conditions. In the University of Cape Town (UCT) process for combined nitrogen and phosphorus removal, polyphosphate-accumulating bacteria will also be exposed to nitrate in the anoxic zone, i.e. an electron acceptor that may be utilized as well as the oxygen of the aerobic zone. During a 1-year study of the full-scale UCT process run at Öresundsverket, Helsingborg, special attempts were made to quantify the relative contribution of an anoxic phosphate uptake at full-scale conditions: the dominant chemical oxygen demand (COD) uptake in the anaerobic zone could be identified as poly-β-hydroxy-alkanoates (PHA). PHA accumulation was at its largest during a test period with acetate added as an extra carbon source. At least one-third of the COD consumed in the anoxic zone could be identified as PHA. The anoxic sludge contained increased amounts of polyphosphate and reduced amounts of free orthophosphate compared to the anaerobic zone, approaching the levels of aerobic sludge. The metal bound orthophosphate remained largely unaffected, at a level of 25–30% of the total phosphorus content. After correction for the sludge recycling of the system, the formation of inorganic polyphosphate in the anoxic zone itself was estimated to be 30% of the total. When the metabolic activity was tested under controlled conditions in batch, the anaerobic sludge of the plant showed a high denitrifying activity accompanied by a phosphorus uptake and a simultaneous consumption of intracellular PHA corresponding to 2 g-COD/g-N, i.e. half the theoretical value needed for denitrification when biomass growth is included. It is concluded that intracellular PHA played a major role as a carbon source for denitrification in this full-scale UCT process, with a corresponding phosphate uptake also in the anoxic zone. The biological nitrogen and phosphorus removal must, therefore, be regarded as interconnected.

Internal energy-based competition between polyphosphate- and glycogen-accumulating bacteria in biological phosphorus removal reactors—Effect of [formula omitted] feeding ratio

In acetate-fed, anaerobic-aerobic alternated bioreactors, the P C feeding ratio (wt/wt) was found to be a key factor influencing an “internal energy-based” competition between polyphosphate-accumulating bacteria (PAB) that mediate biological phosphorus removal and glycogen-accumulating bacteria (GAP) that do not. Both groups were previously known to use internally stored polyphosphate and glycogen, respectively, as energy sources for storing acetate as polyhydroxyalkanoate in the anaerobic stage, and to use the reserved material for growth in the aerobic stage. When excessive P was provided ( P C feeding ratio = 20 100 ), PAB could accumulate a high content of polyphosphate, and with a higher and faster acetate uptake ability, successfully out-competed GAB. In contrast, reduction of the P C ratio to 2/100 caused the depletion of the polyphosphate content in PAB, eventually leading to a replacement by GAB as the majority. Stable coexistence of both groups occurred under operation with a median P C ratio, because the stored energy pool of PAB was not enough for the complete uptake of acetate under anaerobic conditions. Thus, GAB could share what acetate remained, coexisting with PAB. These competitive outcomes were strongly supported by results on the anaerobic metabolism of acetate, and by microscopic observations in this study.

Glycogen accumulating population and its anaerobic substrate uptake in anaerobic-aerobic activated sludge without biological phosphorus removal

The presence of a glycogen accumulating population and its abilities of substrate uptake and storage in anaerobic-aerobic activated sludge fed with mainly acetate were investigated. Because a low phosphorus/carbon feeding ratio (2/100, wt/wt) was used to suppress the growth of polyphosphate-accumulating bacteria, the sludge exhibited no biological phosphorus removal activity. Still, under anaerobic conditions, acetate, propionate, butyrate, valerate, pyruvate, lactate, most key intermediates in the tricarboxylic acid cycle, and gluconate were taken up and stored as polyhydroxyalkanoate (PHA); and glucose, fructose, maltose, sucrose, trehalose, and raffinose as cellular glycogen and PHA. The energy and reducing equivalents required for the carbon uptake and storage were generated from the glycolysis of either cellular glycogen or a sugar taken up. Results of substrate uptake further suggested that the sludge preferred to utilize glucose instead of cellular glycogen as an energy source during acids uptake. Different morphological types of bacteria with deposits of cellular PHA granules after substrate uptake were observed as the majority in the sludge, suggesting that they could assimilate or possibly scavenge most of the dissolved substrate of the waste water and dominate in the deteriorated biological phosphorus removal processes.